Study in Sweden

The study was conducted by Anders Ek and was supervised by Dr. Karin Piehl-Aulin. The author realizes that the number of skiers tested is small but due to time and scheduling constraints it had to be limited.

BACKGROUND

There has been a great deal of criticism of roller skis because they roll too easily and do not provide sufficient resistance for proper training. Exercise Physiologist Dr. Artur Forsberg stated that conditioning is a consumable resource that must continuously be replenished. In order to increase cardiovascular capacity there must be increased load on the system. The increased load can be achieved by more training and / or by greater intensity. Training has a central and localized effect. The central training requires the use of large muscle groups in an aerobic state. This develops the heart muscle, the lungs and the capability of the blood to absorb more oxygen.

However, the muscle development is dependent on the specific form of training. This is referred to as the localized muscle effect. Specific training develops and changes muscle mass, enzyme activity, slow and fast twitch fibers, mitochondria and capillary action and energy conversion.

Some skier’s train many hours by using roller skis that have minimal rolling resistance and often-on terrain that is relatively flat compared to a XC racecourse. With minimal exertion it is thus easy to train many hours without much specificity and without sufficient load on the central system when compared to skiing on snow on a XC racecourse.

We know that long training passes are required, but we must also look at the quality of training. To increase oxygen uptake we need training that will generate at least 60-70% of max VO2. If the skis roll too easily and the terrain is too flat the resistance for proper training is insufficient. If we compare X-C skiers with other endurance athletes we know that X-C skiers have the highest VO2 values, especially if we measure ml/kg x min. However, today skiers need more than maximum oxygen uptake. Other important areas are anaerobic capacity, strength, technique and tactics.

Development of roller skis has resulted in models with more resistance. The V2-910 is presently the slowest ski made by Jenex Inc. and this study was undertaken to determine how this roller ski compares to real skiing.

SKIERS IN THE STUDY

Six Junior skiers, one girl and five boys age 15 and 16, participated in the program. Treadmill tests were performed to determine VO2 values and maximum pulse rates.

NAME, WEIGHT KG., MAX VO2, MAX PULSE

TL* 60 -------------- -----------------

JN 65 68 192

KG 45 62 200

MH 65 76 198

TS 58 70 195

AN 58 49 197

*TL could not participate in the treadmill test due to sickness.

TEST SITE

The tests for both skiing and roller skiing were performed on the same place and on the same courses. The paved roller ski area was the snow skiing area in the winter. The length of the course for distance testing and warm up was 3,400 meters and consisted of three laps. For race speed testing the course was 2,500 meters with two laps.

The tests were performed only with classic technique. Lactic acid values were measured directly after the distance workout and directly after the speed workout and also 3 minutes after the maximum tempo race speed test. Pulse rates were monitored using Polar Sports testers. After each workout the participants were asked to rate their effort according to the Borg perceived effort scale. First the skiers did a distance and warm up workout. The skiers were asked to ski at a pace that was typical for a long slow distance workout, but to only ski for 10.2 kilometers. After a ten-minute recovery period the skiers were asked to ski 5 kilometers at race pace.

The snow test was done in the beginning of March. Conditions were excellent with well-prepared tracks and new snow with a temperature of -4C (24F). In the middle of May the same course was skied on roller skis. Conditions were again excellent with sunshine, no wind and the temperature was 20C (68F).

SLOW LONG DISTANCE TRAINING SPEED (10.2k)

NAME & TIME FOR SNOW SKIS & TIME FOR ROLLER SKIS

TL 45.00 41.25

JN* 43.18 --------

KG 45.05 43.55

MH 40.55 42.40

TS 44.00 49.55

AN 45.55 44.30

*JN could not participate in the roller ski test due to a fracture in his foot.

Somewhat mixed results. Two were faster on skis, three faster on roller skis. This was TS first roller ski of the season and his balance on roller skis during the warm up was somewhat shaky.

PULSE

NAME, PULSE SKIING ON SNOW & PULSE ROLLER SKIING

TL 168 169

JN 163 -------

KG 167 164

MH 167 164

TS 167 152

AN 175 162

LACTATE LEVELS

NAME, MMOL/L SKIS, MMOL/L ROLLER SKIING

TL 4.6 4.7

JN 1.3 ------

KG 1.1 1.4

MH 1.5 1.8

TS 1.8 1.8

AN 1.6 2.1

RACING SPEED (5k)

NAME, TIME SKIING, TIME ROLLER SKIING

TL 17.00 16.45

JN 16.58 ------

KG 16.32 16.55

MH 16.05 15.05

TS 16.03 16.30

AN 18.26 18.05

The times are very close except for MH who was one minute faster on roller skis.

PULSE

NAME, PULSE SKIING, PULSE ROLLER SKIING

TL 190 194

JN 191 ------

KG 196 198

MH 193 195

TS 189 185

AN 187 196

LACTATE LEVELS

SKIING & ROLLER SKIING

NAME, MMOL/L

At finish and 3 minutes later. Skiing on snow & roller skiing

TL 10.7 10.2 11.3 9.3

JN 7.2 7.5 -----------------------------

KG 14.3 10.7 9.0 8.9

MH 10.9 10.1 11.0 9.0

TS 10.5 9.4 5.9 5.5

AN 5.7 4.9 6.6 5.7

BORG PERCEIVED EFFORT SCALE

After the race speed test the skiers were asked to rate the perceived effort according to the Borg scale.

SKIING vs. ROLLER SKIING

TL 19 19

JN 16 ------

KG 17 19

MH 14 16

TS 18 18

AN 16 18

Here we can see that two rated skiing and roller skiing equal while three felt roller skiing was harder. The roller ski test was done in May when roller ski season had just started while the snow skiing was done in March. I expected that roller skiing would be much faster and easier than skiing on snow, but the results of the racing speed test show that the rolling resistance on the V2-910 is very much like skiing on snow and we consider the V2-910 an exceptional ski specific training device. Anders Ek.

The commentary below is by Len Johnson

To me the most interesting aspect of Ander's study is that the course for skiing and roller skiing is identical so that you can eliminate one of the largest variables when comparing snow skiing to roller skiing.We really can’t tell very much from the distance-training warm up workout because the participants were asked to duplicate a long slow distance workout for only 10.2 kilometers and they had been asked to pace themselves accordingly. It’s very obvious that the skiers paced themselves very differently.

The racing speed test is much more meaningful because you are trying to go as fast as you can for five kilometers and here the skiing on snow and roller ski results are almost identical, except for MH who was 1 minute faster on the roller skis.

The skiers had only a ten-minute rest after the 10.2k distance warm up. MH was the second fastest skier in the on snow race test and has a VO2 max of 76, which is very high for a 15 year old. During the distance warm up he was going quite slow and was undoubtedly more rested than the others. TL, who in the snow racing 5k test was almost a minute behind MH, was skiing 1’15” faster than MH in the roller ski warm up and was probably more tired than MH during the race portion of the roller ski test. However, TL still roller skied slightly faster than he skied on snow. TS, who was roller skiing for the first time this season, was extremely wobbly and slow in the warm up distance ski, but still managed to be only 27 seconds slower than on snow in the race speed test. If the roller ski test had been done in the end of June, when the participants had another six weeks of roller skiing, I am positive that all of them would have been faster on roller skis.

When we look at our sales records of classic roller skis we find that most people are buying our faster classic skis and most coaches are suggesting that the young skiers use our faster models, generally the 930. One of the reasons that many young skiers use the faster roller skis is because so many we have talked to think that skiing on snow is faster than roller skiing. But as can be seen in the above study even our slowest skis are slightly faster than skiing on snow. So why are so many coaches putting skiers on roller skis that do not equate to the resistance of skiing on snow?

Artur Forsberg's study in the mid 80's showed that the Swedish Junior skiers that were using fast roller skis for training were not as fit as the Junior skiers of the late 70's and early 80's that were using slower roller skis and running more. The Junior skiers of the 70's and early 80's included World and Olympic Champions Gunde Svan, Thomas Wassberg and Torgny Mogren. (Some of the best skiers in the history of the sport.)

Jim Galanes knows from a study he made many years ago that so called “slow” roller skis are still faster than skiing on snow. I also know from my own testing that our slowest model, the V2-910, is just slightly faster than skiing on snow. Our driveway in NH is a gradual climb of almost 800 feet and the driveway goes through a field. For several years I timed myself skiing on roller skis in the driveway and in the winter made a track in the field and timed myself over the same terrain. Roller skiing was always slightly faster, but the V2-910 is very close to the speed of skiing on snow.

The elite skiers always used the slowest skis for training. John Bauer, Kris Freeman and Olympic Champions Vladimir Smirnov and Kristina Smigun trained on V2-910’s as do a lot of the top World Cup athletes. We can make the wheels on the 910 even slower and recently the highly respected French coach Claude Prica asked us to make extra slow wheels for some of his athletes.

I don’t know what roller skis Olympic Champion Kalla is using, but in a Swedish article she said that roller skis do not provide enough resistance for a good workout so instead of roller skiing she preferred to run. (Have to get her a pair of very high resistance skis. We can now put 2-ISR speed reducing units in the free wheels of V2 skis and make the roller skis equal to skiing in slow snow conditions. That’s what we did for Claude Prica, the French coach. Think Kalla would like the skis with 2-ISR because they would replicate skiing on slow snow.)